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Structural,vibrational and magnetic properties of Ti substituted bulk hematite:-Fe_(2-x)Ti_(x)O_(3)

Journal of Advanced Ceramics 2014年第4期3卷 269-277页

作者： Dinesh VARSHNEY arvind yogi Materials Science Laboratory School of PhysicsVigyan BhawanDevi Ahilya UniversityKhandwa Road CampusIndore 452001India School of Physics Indian Institute of Science Education and ResearchThiruvananthapuram 695016India

Ti doped hematitea-Fe_(2-x)Ti_(x)O_(3)(x=0.0,0.0206 and 0.0344)samples are synthesized using solid-state ceramic route *** phase and corundum(Al_(2)O_(3))type structure is revealed from the X-ray diffraction(XRD)*** substitution of Ti at Fe site,all Raman active modes are shifted to higher wave *** additional feature of Eu(LO)mode at about 660 cm^(-1)is *** E_(u) mode frequency is decreased and pronounced systematically as a function of Ti doping,and it reaches a value of 658 cm^(-1)for x=*** coercivity Hc(remanence M_(r))for x=0.0,0.0206 and 0.0344 are determined to be 995 Oe(0.44 emu/mg),1404 Oe(0.00019 emu/mg)and 2023 Oe(0.00016 emu/mg),*** larger coercivity for Ti doped samples can be attributed to their enhanced shape and magneto-crystalline *** observed isomer shift(d)from room temperature Mössbauer data clearly shows the presence of ferric(Fe^(3+))and Ti^(4+)ordering ofa-Fe_(2-x)Ti_(x)O_(3)for x=0.0344.

关键词： magnetic materials X-ray diffraction(XRD) Raman spectra Mössbauer spectroscopy

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Magnetic and structural properties of pure and Cr-doped haematite:α-Fe_(2-x)Cr_(x)O_(3)(0≤x≤1)

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Journal of Advanced Ceramics 2013年第4期2卷 360-369页

作者： arvind yogi Dinesh VARSHNEY Materials Science Laboratory School of PhysicsVigyan BhawanDevi Ahilya UniversityKhandwa Road CampusIndore 452001India School of Physics Indian Institute of Science Education and ResearchThiruvananthapuram 695016India

Solid-state ceramic technique route is used for synthesizing Cr-doped haematiteaα-Fe_(2-x)Cr_(x)O_(3)(x=0,0.125,0.50 and 1)*** phase and corundum(Al2O_(3))type structure is revealed from the X-ray diffraction(XRD)*** Raman spectra ofαa-Fe_(2-x)Cr_(x)O_(3)illustrate seven phonon *** substitution of Cr(x=0,0.125,0.50 and 1)at Fe site,all Raman active modes are shifted to higher wave *** coercivity and remanence of Cr-doped haematites increase as x *** increased coercivity and remanence for Cr-doped samples can be attributed to their enhanced shape and magneto-crystalline *** observed isomer shiftδdvalues from room-temperature Mössbauer data clearly show the presence of ferric(Fe^(3+))and Cr^(3+)ions illustrating strong ferromagnetic ordering up to x=0.125 inaα-Fe_(2-x)Cr_(x)O_(3)haematite and weak ferromagnetic ordering foraα-Fe2-xCrxO_(3)(x>0.125)haematites.

关键词： magnetic materials X-ray diffraction(XRD) Raman spectra Mössbauer spectroscopy

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Alkaline Earth (Ca) and Transition Metal (Ni) Doping on The Transport Properties Of Y1-Xcaxba2(Cu1-Yniy)3O7-δSuperconductors

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Journal of Modern Physics 2011年第8期2卷 922-927页

作者： Dinesh Varshney arvind yogi Neha Dodiya Irfan Mansuri 不详

We report the results of dc resistivity, ac susceptibility, and thermopower study of partial substitution at Y (A site by Ca) and at Cu (B site by Ni) polycrystalline superconductors. The iodometric analysis reveals that the oxygen deficiency,δ,for YBa2Cu3O7-δ(S-I),Y0.9Ca0.1 Ba2Cu3O7-δ(S-II),Y0.8Ca0.2Ba2Cu3O7-δ(S-III) and Y0.9Ca0.1 Ba2(Cu0.99Ni0.01)3O7-δ(S-IV) samples are 0.16, 0.30, 0.39 and 0.29 respectively. The x-ray powder diffraction pattern indicates that all samples are in orthorhombic phase. The dc resistivity, ac susceptiblity and the thermopower measurements shows that the divalent Calcium doping at the trivalent Y site and transition metal Ni doping at Cu site causes a suppression of the superconducting transition temperature (Tc) from 89 to 81 K. The ac susceptibility confirms the ferromagnetic to antiferromagnetic phases at a defined Tc. The room temperature S value increases for Ca substituted YBa2Cu3O7-δwhile to that it decreases for Y0.9Ca0.1Ba2(Cu0.99Ni0.01)3O6.71. The above feature is an indicative of enhanced number of mobile holes for the Ca doped YBa2Cu3O7-δ, while to that the charge carrier density is reduced in simultaneous A (Ca) and B (Ni) site doped sample.

关键词： Y-Based Superconductors Doping Effect Transport Properties

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